Transmitting and receiving apparatus for wireless telegraphy



,- Mm?) 1923; I v

' G. H. CLARK TPQA'NSMITTING AND RECEIVING APPARATUS FOR WIRELESS TELEGRAPHY F d March 1921' 4 sh t -shebfr Jufly 17, 19230 G. H. CLARK TRANSMITTING AND RECEIVING APPARATUS FOR WIRELESS TELEGRAPHY Fi led March 1921 4 Sheets-Sheet 2 ill! A amoewt o'c IRA/L v630366212ZZAYIYIY $511 6? Jul 17,1923. 1,461,754

G. H. CLARK TRANSMITTING AND RECEIVING APPARATUS' F OR WIBELESSTELEGRAPHY Filed March 5, 1 921 4 SheetS- -Sheet 5 wmmhoz GEOEGE Hf 6171131! 351 M Wow L G. H.'CLARK TRANSMITTING AND RECEIVING APPARATUS FOR WIRELESS TELEGRAPHY Filed March '5, 192i 4 Sheets-Sheet 4 Patented July i7, i923}.

at in innate GEORGE E. CLARK, OF BROOKLYN, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A. CORPORATION OF DELAWARE.

TRANSMITTING AND RECEIVING APPARATUS FOR WIRELESS TELEGRAPHY.

Application filed March 3, 1921. Serial No. 449,394.

.To all whom it may concern:

Be it known that I, GEORGE H. CLARK, a citizen of the United States, and a resident antenna.

of Brooklyn, N. Y., have invented certain .a specification accompanied by drawings.

This invention relates to transmitting and receiving apparatus for wireless telegr'aphy. One object is to increase the speed ofsignal transmission by means of the Morse, or similar code without running the dots and dashes together.

Another object of the invention is to cause the quick dying out of the current at the end of each dot or dash when the signal is being transmitted so that sharp dots and dashes will be sent from the transmitting station.

Still another object of the invention is to cause the current, induced in the receiving apparatus by the electromagnetic waves, to die down very quickly so that there will be no tailing out at the ends of the dots and dashes.

Other objects will appear in the following description, reference being had to the drawings in which:

Fig. 1 is a conventional illustration of a transmitting station for emitting sharp dots and dashes.

Fig. 2 is'a modification of theinvention.

Fig. 3 is a further modification.

Fig. 4 is an additional modification of the invention.

The invention is applicable to both dampedand undamped type of transmitting apparatus but for clearness of illustration the principles will be explained in connection with C. W. or continuous wave transmission. When a signal key of a wireless system is released the current does not die down in the antenna immediately but tapers or tails ofi in oscillatory form.

This therefore transmits the dot or dash of the signal not as a sharp and well defined interruption of the wave but as a more or less gradual interruption so that when the signal wave leaves the transmitting antenna it is already in such form as to cause a more or less indistinct termination ofv the dots or dash when the wave reaches the receiving This makes the dots and dashes longer than necessary and slows down com munication.

At -the receiving station the electromagnetic wave ceases to impinge. on the antenna at the end of each dot and dash but the current does not stop instantly; It dies down as a damped oscillation. This tends to make the termination of each dot and dash mitting antenna should have instant cutting oil of the signalling'current there would be a tailing out effect in the receiving coil due to the dying down or" the electromagnetic field in the oscillatory circuit of the receiving apparatus. In my invention I provide means for annulling this tailing out effect in the receiving system and I accomplished this result by sending out a counter wave from the transmitting'station that more than annuls the dying down current at the end of each dot or dash and produces an electromagnetic wave 180 from the main wave but this is brought into effect only at the end of each dot or dash. This opposed electromagnetic wave tends to induce a current that is out of phase with the dying down current and the combination of the two effects results in sudden termination of the dots and dashes.

The invention therefore has two aspects one consisting of means at the transmitting station to causethe waves to die down veryquickly and the other consisting in means for sending out from the transmitting station at the end of each dot or dash a counter wave that will annul the tailing out effect in the receiving circuit due to the dying down of the electromagnetic or electrostatic field in the receiving system.

One way of accomplishing the transmission of sharp dots and dashes is shown in he provided". .When the key 6 is depressed for the transmission of a dot or a dash of a message, contact is first broken at the point 7 which opens the circuit of saturation coil Son the magnetic amplifier. The impedance of the magnetic amplifier 5 is thereby very greatly increased and it no longer loads ,up the alternator; The alternator therefore sends continuous-waves into the antenna. Simultaneously or immediately following the opening of the contact at 7- the contact 9 is opened, which deenercontact screw 28.

gizes the magnet or solenoid 10. Switch contact 11 closesand resistance 12 is short circuited.- At the end of the dot or dash of the signal, pressure is removed from the telegraph key 6 and in the return movement contact 9 is closed. This results in the removal of the short circuit around the resistance .12 so that whencontact is closed at 7 to-stop the signal, the dying down of the current is made quite rapld. In other words, the dying out oscillation is very strongly'damped by the resistance 12. In this way the transmitted signals terminate quite sharply as compared to signals transmitted in the old way and higher speed of transmission can be had without running the dots and dashes of the signal together;

The action of the magnetic amplifier 5' is well understood in the art, and it is shown conventionally only. In general, it may be said that when contact 7 is closed the core is saturated by the current flowing in the coils and the reactance ofthe shunt circuit 13 is very greatly reduced. Since this circuit is in shunt to the alternator 4, it puts a heavy drain on it and pulls down the voltage to such an extent that practically no current is sent into the antenna. Therefore, closing contact? interrupts the signal by terminating the dot or dash. When contact 7 is broken by pressing the key 6 downward the saturation effect of the direct current from battery 14 is-eliminated and the reactance of themagnetic' amplifier 5 is very high. I This therefore removes the shuntcircuit load on'the alternator so that its voltage rises to normal-value and current is sent into the antenna to produce the dot or dash of the signal. 7

There are various other ways of accomplishing the sudden termination of the ourrent at the end of each dot or dash, one other embodiment of the invention being shown in Fig. 2. Twoalternators 14, 15-,

are coupled together [so that the voltages are 180 apart, that is; the voltages are of opposite phase. When key 16 is depressed, contact is made at 17, which energizes magnet 18 from the current of battery 19. Switch 20 is thrown over into engagement -with contact 21 and the antenna 22 is connected to ground through the secondary of transformer 23. Current is therefore sent intothe antenna from the alternator 14 to produce the dot or dash of the signal. On the downward strok of the key 16, as just referred to, switch ar'm25 first engages insulation section 26 and further movement rotates this arm about its pivot point .27

and out of engagement with adjusting screw 28. As the key travels further downward the switch arm 25 passes off of the insulation 26 and on to thev contact strip 29. No current however is sent through the magnet 30 as the circuit is open at the point of the When the operator releases pressure from key l6'to terminate the dot or dash of the signal the initial movement rotates the arm 25 about the point 27 on account of friction against strip 29. The circuit is therefore closed through contact 28 and the switch magnet 30 substantially at the same time that contact is open at 17 of the key. This pulls the switch arm 20 over into engagement with contact 31 and the antenna is then connected through the secondary of coupling coil 32 of alternator 15 which tends to put a current of short duration into the antenna 180 vout of phase with theoriginal signalling current. This therefore opposes the continuation of the dying out oscillations and the dot or dash is brought to a more abrupt close.

As the key 16 moves on up afterpressure is released, contact arm 25 again engages insulation 26 and the circuit of magnet 30 is lnterrupted. It will therefore be seen that after the main alternator is disconnected from the antenna to terminate the dot or dash that an E. M. F. of opposite polarity is suddenly thrown onto the antenna to guickly terminate the dot or dash. However prefer to so adjust the opposing voltage and its duration to be more than sufiicient to terminate the dot or dash. That is I adjust it so that a counter current is sent into the antenna to produce a counter wave in the ether that will proceed to the receiveing stat1on and tend to generate an opposing current in, the receiving apparatus of opposite antenna, During the transmission of the main wave this resistance was short circuit- The telegraph key can be suitably adjusted as to the closing of the contact 17 by means of some adjustment such as screw 33, and the point at which the switch 25 engages insulation 26 or the contact strip 29 can be adjusted by means of screws 34, 35. The position of the two strips 29 can then be adjusted by sliding the screws 34, on theslot 35 of member 36. Also the duration of the closure of the curcuit through magnet 30'can be regulated by these same adjustments.

Thecircuit arrangements of Fig. 2 are made diagrammatic for ease of understanding but it will be understood that in practice the alternators may be controlled by magnetic amplifiers such as shown in Fig. 1 or by other means'of efiicient control of the signallin current.

In ig. 3 only one alternator is used. Oppositely wound transformers are adapted to be connected to the alternator and these con stitute the source of opposed E. M. F.s. Pressure on telegraph key 36 closes contact 37 and energizes switch magnet 38' from battery 39. Contact 40 is therefore closed and the alternator 42 sends signals into the antenna 43 through transformer 44. When pressure was applied to key 36 contact was also closed at point 45 of the key and solenoids or magnets 46, 47 were energized from battery. 39. By regulating the time constants or by proper spacing of the switch parts, bell crank switch arm 48 will be pulled out of position before contact arm 49 engages it inits upward travel under the pull of' energized solenoid 46. No contact is therefore made in the circuit connected to this switch arm at this time. -At this time contact between switch arm 49 and adjustable contact spring 49' is broken and this doenergizes magnet 50. Damping resistance 51" is therefore short circuited.

When pressure is removed from contact 36 to terminate the dot or dash the circuit is broken at contact 37 as well as at contact 45. The opening of the contact 37 de-energizes magnet 38 and disconnects the alternator 42 to the antenna through the trans former 44 and the opening of the contact at 45 de-energizes both magnets 47 and 46. Spring 50 throws the bell crank 48 back into operative position and in the downward movement of switch arm 49 under influence of spring 51, contact is closed between the arms 48 and 49. This energizes solenoid or magnet 53, which connects the alternator 42 to transformer 54. By reversing the connection of this transformer with respect to transformer 44 an E. M. F. of reverse phase is applied to the antenna and a correcting wave is sent out from the antenna to be transmitted to the receiving station to kill out the persisting current in the receiving apparatus, as previously described. The correcting wave is suddenly terminated in the antenna by insertion of damping resistance 51. This is brought about by closure of contact between arm 49 and contact spring 49 at the end of the downward movement gizes can be controlled in any way but in the example shown in Fig. 3 of the drawing this adjustment is accomplished by the leakage valve 57 in the dash pot 58. In this connection it will be understood that in the upward stroke of switch arm 49 the valve 59 in the dashpot 58 opens and permits free movement while stroke of the switch arm this valve closes and leakage occurs only through valve 57 or by any other equivalent means. Adjusting screws 52 permit of additional adjustments of the' contact arm 48 on the bell crank to control the duration of the reverse wave and adjusting screw 55.permits adjusting the time of removal of the short circuit around resistance 51. I

v In Fig. 4 I have shown an are 60 as the primary source of oscillations. The details of this need no explanation as they are well known in the art. The source of oscillations is connected to circuits containing the oppositely wound primaries 61 and 62 of a transformer having a rotatable secondary coil 63.

By reversing one primary with respect to into the field of the transformer primary of circuit 62. During the downward movement of key 65 the rear portion 68 of the key slides over-the projection 69 on switch arm 70. This final upward movement of the switch arm 70, closes the circuit through switch coil 71, but since the armature '72 was in the downw'ardpreviously pulled over by coil 67 the closure of the circuit through coil 71 has no eflect at this time.

When the operator releases-pressure on key 65 contact is opened at 66 and magnet 67 is de-energized. Energizing coil 71 therefore immediately pulls the armature 72 to the left and coil 63 is rotated out of the field of coil-62 and into the field of coil 61. An

E. M. F. of opposed phase is then sent into the antenna to send out a counter electromagnetic wave for sharpening the dots and dashes at the receiving station as previously described. The duration of the closure of the circuit through coil 71 .is momentary as the end 68 of the key releases spring 70 as soon as it engages cam stop 74, and it springs back into the position shown in full lines. The duration of the contact closure can be varied by adjustment of the cam stop 74. At the end of the upward stroke of the front lever of key 65 contact lSClOSGd at 65 and this energizes magnet I 66 which inserts "sharp damping resistance 67 in the antenna to qu'ckly'terminate the counter wave. e "le I have shown anumber of different embodiments of my invention it will be apparent that other modifications ma be employed to sharpen the dots and ashes of the signal without departing from the spirit of the invention.

Having described my invention what I claim is:

' 1. The method of caus'in the sudden termination of radio signa ing oscillations which consists in inducing oscillations of opposite phase in the receivin circuit tooppose the continuation of oscifiations due to the stored energy in the receiving circuit.

2. The method of wireless signalling which consists in sending an interrupted wave comprising a train of oscillations from the transmssion station to constitute the sig nal and sending a correcting wave comprising a train of oscillations substantially 180 out of phase-with the first train at substantially the end of the interrupted portion to cause the end of the portion of the wave iniduced in the receiver circuit to terminate 3. The method of wireless Signalling which consists insending an interrupted wave comprising a plurality of oscillations from the transmtting station to constitute the signal, sending a pluralit of opposing oscillations at substantially t e end of theinterrupted portion and suddenly terminating'the opposing wave'to cause sharp signal interruptions in the receiving circuit.

4:. The method of wireless signalling .-which consists in sending dots and dashes oi the signal wave, each signal consistlng of a: group .of oscillations,'sendin a counter wave cons sting of a group of osci lations substantially out of phase with thes'ignal oscillations at substantially the end of each dotand dash and suddenly terminating each counter wave to cause sharply defined dots and dashes in the receiving circuit."

5. In wireless signalling systems, an an tenna, a generator of oscillations, means for causing interruptions in the signal oscillaelectro-motive force into the antenna at substantially the end of the interrupted portionsof the signal.

' '6. In wireless signalling systems, an antenna, a generator of oscillations, means for causing interruptions in the signal oscillations, means for sending an opposing electro-motve force into the antenna at substantially the end of the interrupted portions of the signal and means to suddenly terminate the ofiposing electro-motive force.

7. wireless signalling systems, an antenna, a generator of signal oscillations, a generator of opposingoscillations, a resistance adapted to be inserted into the antenna,

said resistance into the antenna when the- .source of opposing oscillation is discon nected.

.50 tions, and means for'sendin'g an opposing an. CLARK. 

